In Situ CL-Out Bioremediation of Industrial Solvents

Case Study :

Industrial Manufacturing Site, Illinois

Remediation Summary

Leaks from an aboveground solvent tank impacted soil and ground water quality at a manufacturing site in Illinois.  The impact was found under the adjoining building as well as the area near the tank.  The soil and ground water were treated in situ with CL-Out® bioremediation microbes.  Through cometabolism CL-Out® microbes reduced the contaminant concentrations to acceptable levels in less than one year.

Contaminants Soil Results (mg/Kg) Ground Water Results (mg/L)
Pre-Treatment Post- Treatment Pre-Treatment Post- Treatment
PCE 41.8 1.69 5.59 0.006
TCE 4,670 632 15.6 0.026
Cis 1,2-DCE 171 56.6 7.43 0.029
Vinyl Chloride BDL BDL 0.095 0.013

Implementation and Results

Soil Type:  Silty clay till

Treatment Area:  15,000 sq. ft.

Unsaturated soil thickness:  16 ft.

Saturated aquifer thickness:  5 ft.

Treatment: Two applications, initial treatment with 13 units of CL-Out® and follow up treatment with 5 units.

Product Cost: $30,000

Conclusions

CL-Out® bioremediation quickly and cost-effectively reduced the contaminant concentrations to acceptable levels.  Through cometabolism the parent and daughter products were removed simultaneously.  CL-Out® bioaugmentation accelerated the site remediation and reduced uncertainty by applying the right microbes where they were needed.

Aerobic Cometabolism of PCE at an Industrial Site in Tampa, Florida

Project Summary

Degreasing solvents were found in the ground water at an industrial manufacturing facility in Tampa, Florida.  The solvents include PCE and its associated breakdown products. The source of the ground water contaminants was found to be a former water treatment system drain field.  CL-Out® bioremediation was implemented to reduce the volume of contamination in the source area and down gradient. CL-Out® is a consortium of Pseudomonas sp. that produces constitutive enzymes to cometabolize PCE and other halogenated solvents.  Dextrose is added with CL-Out® to provide a substrate for microbial growth.  Application of CL-Out® bioremediation at this site reduced the total chlorinated solvent concentrations as much as 99% in less than 6 months.

Geology and Hydrogeology

The site is located in Tampa, Florida where the geology is characteristically interbedded silt and sand.  The background ground water redox conditions of the aquifer are not known.

Contamination

The PCE and elevated concentrations of daughter products were found in ground water down gradient of the former drain field.  The PCE concentrations were as high as 280 µg/L and DCE concentrations were as high as 4,400 µg/L, which indicates that there was significant contaminant degradation occurring, but the natural degradation stalled at DCE.   Petroleum hydrocarbons were also present in the ground water and may have served as an oxygen sink during the degradation of the petroleum products.

Remediation Design

CL-Out bioremediation was implemented in the ground water to accelerate the remediation of the source area.  A 55-gallon slurry of  CL-Out was injected on February 11, 2003.

Monitoring wells in the source area and surrounding area were sampled to assess the progress of the remediation.   The following table shows the pre-treatment and post-treatment CVOC concentrations in a source area monitoring well (MW-1) near the application of CL-Out.

 Source Area (MW-1)

Sampling Date CVOC Concentrations (µg/L)
  PCE TCE DCE VC
3/28/02 280 750 4,400 BDL
12/19/02 86 120 1,100 BDL
2/11/03 CL-Out Injection
2/24/03 350 280 1,600 BDL
7/7/03 4.6 6.0 63 BDL

RESULTS

After application CL-Out bioaugmentation the chlorinated solvent concentrations in MW-1 decreased by as much as 99%.  Overall the total mass of contamination was significantly diminished by the bioaugmentation in a short period of time to accelerate the natural degradation.

Using Cl-Out to Finish Remediation Following Chemical Oxidation

CL-Out was used to complete the remediation of ground water contaminated by chlorinated solvents from a former dry cleaning site in Rockville, Maryland.  The ground water contamination had migrated from leaking sewer lines to underlying bedrock fractures.  Fenton’s Reagent was first applied to the site, but the PCE concentrations increased due to desorption.  Subsequently, sodium permanganate was applied to the site.  After the application of 5,000 kilograms of sodium permanganate in 50 locations, the PCE concentrations decreased from the post-Fenton’s Reagent high, but was still three times higher than the original concentrations.

The conditions of the aquifer shifted to more aerobic after the chemical oxidation.  CL-Out aerobic cometabolism was applied to remove the residual contamination and accelerate natural attenuation.  CL-Out was applied in one 165-gallon injection followed by the addition of dextrose as a cometabolic substrate. The natural recharge of oxygen and residual iron, sulfate and manganese are believed to be the electron acceptors for the cometabolism.

According to the reporting author, ” bioremediation is very effective at treating chlorinated solvent contamination at the site.”

Click here to view the USEPA Technology Innovation Report.

CL-Out Completes Remediation After Stalled Natural Attenuation

Investigation of an industrial dry cleaners near Philadelphia, Pennsylvania found concentrations of breakdown products of  PCE in the soil and ground water.  The parent PCE presumably was reductively dechlorinated to TCE, DCE and vinyl chloride.  However, since the daughter products DCE and vinyl chloride are more readily degraded under aerobic conditions, the breakdown was incomplete and natural attenuation stalled.  CL-Out was applied with an oxygen supplement to complete the remediation under aerobic conditions favorable for DCE and vinyl chloride bioremediation.

Geology

The geology of the property is interbedded sandy silt, silt and clay layers.  The contamination was found in a shallow silty sand formation that is underlain by a dense clay layer.  A sand layer directly beneath the clay layer was unaffected by the contamination in the upper sand.

Hydrogeology

The perched ground water was within a fill layer, so the hydraulic conductivity was expected to be variable.  Slug testing results showed the hydraulic conductivity in the upper sand ranged from 1.1 to 3.9 ft/day.  The ground water flow direction was consistently toward a local surface stream.  The extent of the contamination plume was approximately 10,000 square feet.

Ground Water Contamination

The contaminants found at the site were mainly TCE and DCE with trace levels of vinyl chloride.  This suite of contaminants indicated that there was natural degradation of the PCE to lesser halogenated compounds.  The maximum concentrations prior to bioaugmentation were 220 ug/L of DCE, 9.2 ug/L of TCE and 31 ug/L of vinyl chloride.

Remediation

CL-Out was introduced into the ground water through one-inch diameter tubing installed using a direct push sampler.  The use of small diameter injection points made the remediation possible without disruption the dry cleaner operations.  Three injection points were installed in the high concentration area.  Additional injection was made in places where shallow soil had been excavated.

The CL-Out injection was a dosing of four drums in December 2005.

Results

Three months after the injection of CL-Out, the DCE concentration dropped from 200 to 54 ug/L.  The vinyl chloride concentration decreased from 31 to 11 ug/L.  After seven months the TCE and vinyl chloride concentrations were below detection limits and the DCE concentration decreased to 2.9 ug/L.

Due to the relatively anoxic conditions, an oxygen supplement was added to support the aerobic cometabolism.  During the active treatment the dissolved oxygen levels increased from 1.9 to 8.5 mg/L.  The CL-Out microbial population was maintained at 200,000 cells per milliliter.

The monitoring results suggest that by supplementing the dissolved oxygen levels, the CL-Out population was maintained for an extended period.  The extended peak of CL-Out population made possible a greater level of contaminant removal.

Clu-In Reports on Aerobic Cometabolism

The US EPA Technology and Field Services Division produced a report on aerobic cometabolism of chlorinated solvents under their Contaminated Sites Clean-Up Information program on February 7, 2019.  This report includes an overview of aerobic cometabolism and guidance on application and monitoring.  Click here to link to the report.

While the report cites the research of Thomas Wood, et. al., it does not include the research demonstrating aerobic cometabolism of PCE.  The following links go to the research on aerobic cometabolism of PCE.

https://www.che.psu.edu/faculty/wood/group/publications/pdf/PCEMixturedeg.pdf

https://www.academia.edu/3299440/Aerobic_degradation_of_tetrachloroethylene_by_toluene-o-xylene_monooxygenase_of_Pseudomonas_stutzeri_OX1

One of the benefits of aerobic cometabolism is the applicability of bioremediation to shallow soil and ground water that may cause vapor intrusion risk at dry cleaners.  Removing the source of the vapors under natural conditions,without business interruption, is the most economical and sustainable solution.

CL Solutions’ CL-Out consortium has been used for bioremediation of PCE and other chlorinated solvents at dry cleaners and industrial sites since 1999.  Contact CL Solutions for information and a site evaluation.